Along with continuing efforts to improve data access speed and decrease power consumption in dynamic random access memory (DRAM), capacitorless memory technologies emerged as an area of interest. Corresponding desires to scale down memory devices created doubt regarding whether the standard one transistor/one capacitor cell design may provide the desired progress. Capacitorless memory relies upon the floating body effect of field effect transistors instead of a storage capacitor to provide a memory cell. Kuo, et al., “A Capacitorless Double-Gate DRAM Cell Design for High Density Applications,” IEEE Int'l Electron Devices Meeting (IEDM) Tech. Dig., 2002, pages 843-846 as well as U.S. Pat. No. 6,632,723 issued Oct. 14, 2003 to Watanabe et al. (hereinafter, Watanabe) describe use of capacitorless memory cells exhibiting a “floating body effect.” Implementing capacitorless memory cells in DRAM may involve using sense amplifier circuitry known to those of ordinary skill. The sense amplifier may use a cross-coupled differential amplifier, which measures the current level into the cell. The differential amplifier may use the current into the amplifier from the cell as one input and a reference current as another input. The current setting of the reference may be determined by statistics and programmed at probe. The output of the sense amplifier may be a standard binary signal (1-0). The floating body cell is not a destructive read and does not require a refresh of the cell at the time of read. Refresh can be chosen at a convenient time for the circuit.
Given the structural complexity of conventional transistors that use a floating body effect in memory cells, numerous photomasks may be involved to produce a suitable device. For example, Watanabe implies formation of the device shown in Figs. 33A-33B as involving no fewer than six photomasks. In the context of the present document, a “photomask” is formed in a photolithographic process typically involving forming a photoresist on a surface, exposing the photoresist, and developing the photoresist to remove selected portions, thus, forming a photomask. After forming a photomask, the surface exposed through openings in the photomask may be etched. Forming a photomask can involve a time and cost intensive process, prompting a desire to reduce the number of photomasks in methods that produce transistors exhibiting a floating body effect, for example, in capacitorless memory devices.